Preparation Of Polyphosphazenes And Research Of Their Controlled Hydrolysis

Polyphosphazenes are linear polymers containing an inorganic backbone which consist of phosphorus and nitrogen atoms with alternating double and single bonds, each phosphorus bearing two side substituents. Polyphosphazenes have the advantages of broad structural diversity, tailored biodegradability, and excellent biocompatibility as biologically functional macromolecules. Because of these, we did the research work as follows: the synthesis of two novel polyorganophosphazenes, poly[(glycino ethyl ester)(allyl amino)phosphazene] and poly[di(carboxylatophenoxy) phosphazene]; the preparation for polyorganophosphazenes materials with controlled hydrolysis properties respectively through chemical and electrostatic reaction; the characterizations for their physical-chemical properties and basic performances. We expected our fundamental research could be helpful for the exploitation of biomedical materials in the future.From poly(dichlorophosphazene), glycino ethyl ester, and allylamine, poly[(glycino ethyl ester)(allyl amino)phosphazene] with different substituent ratios were synthesized. The following structural characterizations confirmed that the polymers corresponded as designed. Through the chemical crosslink reaction of allyl amino groups, a series of crosslinked polyorganophosphazenes could be obtained. Hydrolysis studies in vitro were also performed to compare the crosslinked polymers with linear ones. It was confirmed that crosslinked polyorganophosphazenes had a longer degradable period and the more allylamine substituted at pendant groups, which would result in a higher degree of crosslink, the slower degradation rate was. Thus, a novel degradable polymer with appropriate degradation rate and adjustable surface hydrolysis property was obtained.From poly(dichlorophosphazene) and ethyl p-hydroxybenzoate, fully substituted polyanion based on polyorganophosphazenes - poly[di(carboxylatophenoxy) phosphazene] was synthesized via nucleophilic substitution and hydrolysis reactions. The following structural characterizations confirmed that the polymers corresponded as designed. Through ion crosslink, polyelectrolyte complex nano-particles were prepared with a nature polysaccharide– chitosan under mild conditions. Through further studies, it was confirmed that the nano-particles consisted of a polymer charge neutral core surrounded by a charged shell of excess positive chitosan. With the increase of pH values, the morphology of nano-particles changed from nano-dispersion to flocculation, and to decomposition in the end. We also investigated the mechanism of these transitions for the tremendous potentials in gene vehicles and drug controlled delivery matrices.